Continuity mistake: In the first shot of the movie we see Dorothy and Toto running and as she comes to stop he's at her right. In the next shot he's behind her. (00:02:00)
Continuity mistake: At the start of the film when Dorothy comes running into the farm calling Aunt Em, Uncle Henry has just taken a chick out of a hat, and is placing it into an open coop. Yet when the shot changes his hand is instantly back in the hat taking out another chick. (00:02:15)
Continuity mistake: In the beginning of the movie Dorothy comes running into the farm and starts to, but doesn't completely unfasten the strap around her books. In the next shot the strap is in her hand. (00:02:20)
Continuity mistake: When Dorothy comes running into the farm at the beginning of the movie, there's a lone cow in the pen behind her and a couple of white chickens that she ends up chasing in the direction of the camera as she runs near the house. Two shots later the cow disappears and the white chickens are now in the pen. (00:02:55)
Continuity mistake: In the beginning of the movie Dorothy comes running into the farm and there's an old tire hanging from a tree. Two shots later as she walks away from Aunt Em and Uncle Henry the tire has been moved. The angle at which it hangs has been changed and the piece of rope hanging on the bottom of it is now three or four inches closer to dead center than it was before. (00:03:00)
Continuity mistake: When we first meet the three farmhands Hunk is leaning on the wagon's break pad. In the next shot he's not. (00:03:05)
Other mistake: In the first shot of the movie we see Dorothy and Toto running home. Several shots later when we first meet Hunk, Zeke and Hickory we see the exact same background spot used again behind them. Dorothy was also running in the wrong direction. (00:03:05)
Visible crew/equipment: After we first meet the three farmhands, Dorothy asks Zeke what to do about Miss Gulch. As he walks off to feed the pigs he steps into the camera's shadow. (00:03:20)
Continuity mistake: In the beginning while Dorothy is still on the farm, she walks along the pig pen fence and then falls in. When Bert Lahr picks her up out of there her dress is perfectly clean. (00:03:45)
Continuity mistake: When Hunk hits his hand with the hammer there are two brooms leaning against the barn behind him. In the next shot they're gone. (00:03:45)
Visible crew/equipment: When Dorothy first walks in the pigsty the shadow of the boom mic can be seen moving on the bottom left of the screen. (00:03:50)
Continuity mistake: When Dorothy walks on the pig sty Zeke walks to his right, looks into, than passes the bucket on the right because it's empty. He then picks up the bucket behind it on the bench and proceeds to feed the pigs. He empties the first bucket then picks up the second empty bucket, which is now three quarters full. (00:03:55)
Continuity mistake: As Dorothy walks on the pigsty there are two grown pigs and about eight piglets in there. When she falls in more than 12 grown pigs now appear in the sty. (00:03:55)
Continuity mistake: As Dorothy balances on the pigsty Zeke feeds the pigs. The bucket he passes by on his right is smooth without any ridges on its sides and the bucket he picks up from the bench has a visible indentation about one inch below the rim. He empties the first bucket than picks up the second, which shouldn't have an indentation around it but does. (00:03:55)
Continuity mistake: As Zeke feeds the pigs we see his hankie sticking straight up out of his back pocket. He doesn't touch it but later before he pulls it out after rescuing Dorothy, it's hanging downward and much more is showing. (00:04:00)
Continuity mistake: When Dorothy first walks on the pig sty the piece of wire that tangles around her foot is dead center right between the two fence posts. When we eventually see her fall in, the wire has been moved about a foot to the right. (00:04:00)
Continuity mistake: When Dorothy is walking on the pig sty platform and talking to Zeke, he is pouring the pig feed into something. The amount of feed he is pouring changes between shots. (00:04:00)
Continuity mistake: As Zeke starts to put the feed into the trough there isn't any pig near him. In the next shot a large pig is feeding. (00:04:00)
Continuity mistake: After Dorothy falls into the pig sty Zeke holds his left hand over the right side of his chest. In the next shot his hand is over the left side of his chest. (00:04:20)
Continuity mistake: After Zeke rescues Dorothy from the crowded pig pen, Hickory wipes his face and neck with the rag in his right hand, but then it cuts to another angle, and the rag is suddenly in his left hand. (00:04:20)
Answer: In the film it's left ambiguous. At the end it's strongly implied that she was dreaming. The characters she meets all look like people she actually knows. In the original book, she actually went to Oz.